Aviation maintenance professionals require an extremely broad range of skills, and they are subjected to the pressures of keeping all aircraft in revenue service, working during evening hours under severe time constraints, maintaining an ageing fleet, and dealing with other factors that affect human performance. The ultimate fear of any maintenance professional (supervisor, AME, apprentice, or inspector) is that an error, once committed, will remain undiscovered and ultimately lead to an accident. The serious consequences of an error in the installation/rigging of flight or engine controls is recognized by both the industry and Transport Canada, thus engine or flight control maintenance is treated differently than other maintenance tasks. The requirement for a second person to formally inspect this work is intended to prevent the aircraft from being dispatched with control problems. In this occurrence, five people had a hand in the installation/rigging/inspection of the elevator trim tab control system of this aircraft, and it was still released with the elevator trim control operating in reverse. The task of hooking up the control cables is, in itself, very basic. There are only two cables and it does not require training to expert levels to understand the system and to recognize that the consequences of hooking the cables up backwards can be disastrous. This analysis will focus on how five aircraft maintenance professionals (with different levels of experience) worked on this system and allowed the aircraft to be dispatched with the elevator trim operating backwards. The job performed by the maintenance crew when they set out to reinstall the horizontal stabilizer and elevator was not technically complex. It involved positioning and bolting the stabilizer and elevator in place and reconnecting and tensioning the elevator trim tab cables. The job was straightforward enough that the crew chief could allow two apprentices to complete it without direct continuous supervision. However, there are a number of seemingly insignificant factors which compounded to make the task more error-prone. First, the crew had been working the night shift for a number of weeks and, since the individuals would revert to a regular daytime schedule on their days off, they had experienced five changes in sleep patterns in the past five weeks, from daytime to nighttime. The control attachment was done at the low point in the circadian rhythm, when each of the individuals involved would be at their lowest level of alertness, suggesting that fatigue may have been a factor in the occurrence.(2) No one on the crew was aware of the degrading effects that shift work has on human performance. The crew chief was simultaneously responsible for assigning and supervising the work of six apprentices that night, a task that would require maximum alertness and awareness on his part. The apprentices, despite low levels of experience, were task oriented. Fatigue would make it more difficult for them to view the project as a whole, compared to the relative ease of viewing and completing a single task. Even during the completion of the individual tasks, fatigue and/or complacency contributed to a number of relatively minor errors in installation, which the lead hand identified during his first inspection. This was an older generation aircraft for which the company had not yet developed a complete set of work or task cards. All maintenance work was performed with reference to the aircraft maintenance manual. The maintenance manual contains detailed instructions on how to remove and install the elevator and how to remove and install the stabilizer, but does not provide instruction for the task of removing and installing the stabilizer with the elevator attached. Thus, a significant amount of interpretation is required. When he connected the control cables, the crew chief had no objective cues to help him decide which cable ends should be attached together. The cables were identical, the turnbuckle locations were not significantly staggered to prevent incorrect installation, and the cables had not been marked when they were disassembled. The crew chief relied on the subjective appearance of the installation, and he believed that they were correctly connected. Comparison with the two- dimensional drawing of the cable installation in the aircraft maintenance manual would not immediately indicate to him that the cables did not cross each other when correctly installed. In fact, after the occurrence, the cable arrangement was described as looking wrong when correctly hooked up and looking right when hooked up backwards. Adding to his false sense of security, he knew that when the controls were rigged, an independent inspection would be carried out. In fact, he had the system double-checked, first by the AME and later by another apprentice. The crew chief's hands-on supervisory style may have been more efficient in getting the job completed, but it prevented the apprentices who were working on the installation from gaining an overall picture of the work being carried out. Although they were in a learning position, there was no formal and little informal technical training for the apprentices. In this instance, there was no explanation of how to choose which of the cable ends were to be connected together, nor was there an explanation of how to ensure that the job was completed correctly. The job was initiated by the crew chief, then turned over to the apprentices to complete. The two apprentices completed the tasks as they thought they had been assigned; they did not feel responsible for the overall installation. This lack of communication was also a factor with the third apprentice who was later assigned to check the rigging. He did not fully understand what he was being asked to do, nor did he appreciate the significance of rigging the controls. His focus was on two of the installation tasks that formed only a small part of the overall rigging procedure. Another significant factor in this occurrence is the quality and quantity of training that the personnel received. The apprentices who carried out much of the work in the installation had never accomplished this task before, a fact that the crew chief was not aware of. Since the continuous and progressive training of the apprentices is not a formal process, he would have been aware only if the apprentices had informed him. The crew chief, who was required to supervise and train the apprentices, had himself never received supervisory training. Training on soft issues, such as supervisory skills and interpersonal communication, is still quite rare in the aircraft maintenance industry. The CARs require that two individuals inspect the control system for correct assembly, locking, and sense of operation, and that both individuals record their signatures in the technical record. There is no requirement that either individual be independent of the work being done. The AME who accomplished the independent inspection did not notice that the controls were incorrectly connected. There are two separate issues relating to this check: the independence of the check, and the contents of the check. The former concept, as outlined in AWM 571.209, was that the inspection would be completed by a person who was completely independent from the persons who accomplished the work. This person would approach the inspection with fresh eyes, and therefore he would see errors overlooked by the person who actually performed the work. He would also have an interest in ensuring that the work was correct since his signature indicates that he is taking on responsibility for work which he did not complete. In practice, the work accomplished is often signed off by one of the AMEs who performed the work, and the independent inspection is signed off by another person working on the same job. This casual attitude toward the signature for the independent inspection is evident in this occurrence. The two AMEs were concerned only that both their signatures were recorded in the logbook, not what their individual signatures represented. Each AME simply signed one of the two blanks on the logbook, regardless of who had done the work and who had inspected the work. The content of the check is also at issue. The intention of the check was to examine for correct assembly, locking, and sense of operation. The AME did check for correct assembly and locking and did find some discrepancies, which he rectified. These are areas he knew the apprentice had completed. He then performed a very cursory inspection of the system, visually checking for full movement of the tab and ensuring that the turnbuckles were not interfering with the pulleys. However, without a second person to assist him, on this aircraft, it was more difficult to adequately check either the range of travel or the sense of operation. Although the captain was licensed and qualified for the flight, his experience on Convair aircraft was extremely limited. When checking the maintenance records prior to the flight, he did note the amount of maintenance work that had been completed on the aircraft, but rather than suspecting potential problem areas, he viewed this as an indication that the aircraft was being kept in great shape. When the aircraft began to pitch nose-up during the take-off run, the crew misdiagnosed the problem as one associated with the aircraft C of G rather than the trim setting.Analysis Aviation maintenance professionals require an extremely broad range of skills, and they are subjected to the pressures of keeping all aircraft in revenue service, working during evening hours under severe time constraints, maintaining an ageing fleet, and dealing with other factors that affect human performance. The ultimate fear of any maintenance professional (supervisor, AME, apprentice, or inspector) is that an error, once committed, will remain undiscovered and ultimately lead to an accident. The serious consequences of an error in the installation/rigging of flight or engine controls is recognized by both the industry and Transport Canada, thus engine or flight control maintenance is treated differently than other maintenance tasks. The requirement for a second person to formally inspect this work is intended to prevent the aircraft from being dispatched with control problems. In this occurrence, five people had a hand in the installation/rigging/inspection of the elevator trim tab control system of this aircraft, and it was still released with the elevator trim control operating in reverse. The task of hooking up the control cables is, in itself, very basic. There are only two cables and it does not require training to expert levels to understand the system and to recognize that the consequences of hooking the cables up backwards can be disastrous. This analysis will focus on how five aircraft maintenance professionals (with different levels of experience) worked on this system and allowed the aircraft to be dispatched with the elevator trim operating backwards. The job performed by the maintenance crew when they set out to reinstall the horizontal stabilizer and elevator was not technically complex. It involved positioning and bolting the stabilizer and elevator in place and reconnecting and tensioning the elevator trim tab cables. The job was straightforward enough that the crew chief could allow two apprentices to complete it without direct continuous supervision. However, there are a number of seemingly insignificant factors which compounded to make the task more error-prone. First, the crew had been working the night shift for a number of weeks and, since the individuals would revert to a regular daytime schedule on their days off, they had experienced five changes in sleep patterns in the past five weeks, from daytime to nighttime. The control attachment was done at the low point in the circadian rhythm, when each of the individuals involved would be at their lowest level of alertness, suggesting that fatigue may have been a factor in the occurrence.(2) No one on the crew was aware of the degrading effects that shift work has on human performance. The crew chief was simultaneously responsible for assigning and supervising the work of six apprentices that night, a task that would require maximum alertness and awareness on his part. The apprentices, despite low levels of experience, were task oriented. Fatigue would make it more difficult for them to view the project as a whole, compared to the relative ease of viewing and completing a single task. Even during the completion of the individual tasks, fatigue and/or complacency contributed to a number of relatively minor errors in installation, which the lead hand identified during his first inspection. This was an older generation aircraft for which the company had not yet developed a complete set of work or task cards. All maintenance work was performed with reference to the aircraft maintenance manual. The maintenance manual contains detailed instructions on how to remove and install the elevator and how to remove and install the stabilizer, but does not provide instruction for the task of removing and installing the stabilizer with the elevator attached. Thus, a significant amount of interpretation is required. When he connected the control cables, the crew chief had no objective cues to help him decide which cable ends should be attached together. The cables were identical, the turnbuckle locations were not significantly staggered to prevent incorrect installation, and the cables had not been marked when they were disassembled. The crew chief relied on the subjective appearance of the installation, and he believed that they were correctly connected. Comparison with the two- dimensional drawing of the cable installation in the aircraft maintenance manual would not immediately indicate to him that the cables did not cross each other when correctly installed. In fact, after the occurrence, the cable arrangement was described as looking wrong when correctly hooked up and looking right when hooked up backwards. Adding to his false sense of security, he knew that when the controls were rigged, an independent inspection would be carried out. In fact, he had the system double-checked, first by the AME and later by another apprentice. The crew chief's hands-on supervisory style may have been more efficient in getting the job completed, but it prevented the apprentices who were working on the installation from gaining an overall picture of the work being carried out. Although they were in a learning position, there was no formal and little informal technical training for the apprentices. In this instance, there was no explanation of how to choose which of the cable ends were to be connected together, nor was there an explanation of how to ensure that the job was completed correctly. The job was initiated by the crew chief, then turned over to the apprentices to complete. The two apprentices completed the tasks as they thought they had been assigned; they did not feel responsible for the overall installation. This lack of communication was also a factor with the third apprentice who was later assigned to check the rigging. He did not fully understand what he was being asked to do, nor did he appreciate the significance of rigging the controls. His focus was on two of the installation tasks that formed only a small part of the overall rigging procedure. Another significant factor in this occurrence is the quality and quantity of training that the personnel received. The apprentices who carried out much of the work in the installation had never accomplished this task before, a fact that the crew chief was not aware of. Since the continuous and progressive training of the apprentices is not a formal process, he would have been aware only if the apprentices had informed him. The crew chief, who was required to supervise and train the apprentices, had himself never received supervisory training. Training on soft issues, such as supervisory skills and interpersonal communication, is still quite rare in the aircraft maintenance industry. The CARs require that two individuals inspect the control system for correct assembly, locking, and sense of operation, and that both individuals record their signatures in the technical record. There is no requirement that either individual be independent of the work being done. The AME who accomplished the independent inspection did not notice that the controls were incorrectly connected. There are two separate issues relating to this check: the independence of the check, and the contents of the check. The former concept, as outlined in AWM 571.209, was that the inspection would be completed by a person who was completely independent from the persons who accomplished the work. This person would approach the inspection with fresh eyes, and therefore he would see errors overlooked by the person who actually performed the work. He would also have an interest in ensuring that the work was correct since his signature indicates that he is taking on responsibility for work which he did not complete. In practice, the work accomplished is often signed off by one of the AMEs who performed the work, and the independent inspection is signed off by another person working on the same job. This casual attitude toward the signature for the independent inspection is evident in this occurrence. The two AMEs were concerned only that both their signatures were recorded in the logbook, not what their individual signatures represented. Each AME simply signed one of the two blanks on the logbook, regardless of who had done the work and who had inspected the work. The content of the check is also at issue. The intention of the check was to examine for correct assembly, locking, and sense of operation. The AME did check for correct assembly and locking and did find some discrepancies, which he rectified. These are areas he knew the apprentice had completed. He then performed a very cursory inspection of the system, visually checking for full movement of the tab and ensuring that the turnbuckles were not interfering with the pulleys. However, without a second person to assist him, on this aircraft, it was more difficult to adequately check either the range of travel or the sense of operation. Although the captain was licensed and qualified for the flight, his experience on Convair aircraft was extremely limited. When checking the maintenance records prior to the flight, he did note the amount of maintenance work that had been completed on the aircraft, but rather than suspecting potential problem areas, he viewed this as an indication that the aircraft was being kept in great shape. When the aircraft began to pitch nose-up during the take-off run, the crew misdiagnosed the problem as one associated with the aircraft C of G rather than the trim setting. There were four maintenance crews maintaining 24-hour coverage via a complicated shift rotation. The crew had been working the night shift for five weeks and were on the second and third nights of a four-night block. The maintenance crew consisted of three licensed AMEs and six apprentices. On the night the cables were connected, two of the licensed AMEs were not at work. The maintenance crew that removed the stabilizer and elevator assembly was not the same crew that reinstalled the assembly. When disconnected, the elevator trim cables were not marked so there were no easy references when they were reconnected. The elevator trim cables were crossed during the installation because the crew chief did not identify the elevator trim cables. When the AME was conducting the final inspection of the installation, he was working alone. Therefore, he relied on operating the trim and checking the movements of the surfaces. He did not notice that the trim tab was moving in the opposite direction to the input in the cockpit. The AME who inspected the installation signed in the maintenance log as having accomplished the work, and the crew chief signed as having inspected the work. The maintenance entry indicated that the elevator trim system had been rigged when it had only been reconnected. The company did not have a complete set of maintenance task cards available for all spontaneous maintenance tasks. To complete this task, the crew were relying on the aircraft maintenance manual. The elevator trim control cable diagram in the aircraft maintenance manual is ambiguous and could be interpreted as having the trim cables crossing each other. Although the company provided adequate technical training for licensed AMEs, there was no training for the apprentices and no human factor or supervisory training for the crew chiefs, nor is there a regulatory requirement for this training. CAR 571.10 requires that two persons inspect any engine or flight controls which have been disturbed (commonly known as the independent or dual inspection). There are no criteria as to who those persons may or may not be. CAR 571.10 does not specifically require that controls be checked for range of travel. Airport ERS were not available for the landing because, after midnight, the airport relies on the municipal fire department for crash fire rescue. To transmit via two-way VHF radio, the crew members had to remove one hand from the control column to depress the PTT button. The captain's inexperience on type, combined with the crew's predisposition toward a C of G problem related to a load shift, led to the crew incorrectly diagnosing the trim problem.Findings There were four maintenance crews maintaining 24-hour coverage via a complicated shift rotation. The crew had been working the night shift for five weeks and were on the second and third nights of a four-night block. The maintenance crew consisted of three licensed AMEs and six apprentices. On the night the cables were connected, two of the licensed AMEs were not at work. The maintenance crew that removed the stabilizer and elevator assembly was not the same crew that reinstalled the assembly. When disconnected, the elevator trim cables were not marked so there were no easy references when they were reconnected. The elevator trim cables were crossed during the installation because the crew chief did not identify the elevator trim cables. When the AME was conducting the final inspection of the installation, he was working alone. Therefore, he relied on operating the trim and checking the movements of the surfaces. He did not notice that the trim tab was moving in the opposite direction to the input in the cockpit. The AME who inspected the installation signed in the maintenance log as having accomplished the work, and the crew chief signed as having inspected the work. The maintenance entry indicated that the elevator trim system had been rigged when it had only been reconnected. The company did not have a complete set of maintenance task cards available for all spontaneous maintenance tasks. To complete this task, the crew were relying on the aircraft maintenance manual. The elevator trim control cable diagram in the aircraft maintenance manual is ambiguous and could be interpreted as having the trim cables crossing each other. Although the company provided adequate technical training for licensed AMEs, there was no training for the apprentices and no human factor or supervisory training for the crew chiefs, nor is there a regulatory requirement for this training. CAR 571.10 requires that two persons inspect any engine or flight controls which have been disturbed (commonly known as the independent or dual inspection). There are no criteria as to who those persons may or may not be. CAR 571.10 does not specifically require that controls be checked for range of travel. Airport ERS were not available for the landing because, after midnight, the airport relies on the municipal fire department for crash fire rescue. To transmit via two-way VHF radio, the crew members had to remove one hand from the control column to depress the PTT button. The captain's inexperience on type, combined with the crew's predisposition toward a C of G problem related to a load shift, led to the crew incorrectly diagnosing the trim problem. The aircraft was dispatched with the elevator trim operating in reverse due to a series of maintenance errors. Contributing to this occurrence were that the crew chief connected the elevator trim control cables in reverse, and that the AME who was tasked subsequently with inspecting the work did not properly assess the sense of operation and trim direction.Causes and Contributing Factors The aircraft was dispatched with the elevator trim operating in reverse due to a series of maintenance errors. Contributing to this occurrence were that the crew chief connected the elevator trim control cables in reverse, and that the AME who was tasked subsequently with inspecting the work did not properly assess the sense of operation and trim direction. Following the occurrence, Kelowna Flightcraft Ltd. proceeded with the change of shift work scheduling to a more workable two week shift schedule. Kelowna Flightcraft Ltd. has amended the maintenance training program to include supervisory training for crew chiefs and plans human factors training for all AMEs in the future. Kelowna Flightcraft Ltd. has amended the independent inspection of flight controls to include the inspection and sign-off by a qualified flight crew member. Following the occurrence, Kelowna Flightcraft Ltd. modified the aircraft so that the PTT button was located on the control column. Kelowna Flightcraft Ltd. has recognized the potential for hooking the trim cables in reverse, and future developments of the model 5800 will be designed with the intent of ensuring that the trim cables are significantly staggered to make it difficult to connect the cables in reverse. Kelowna Flightcraft Ltd. is in the process of writing task cards for the removal of assemblies. These task cards will contain a caution note about trim cable connections. Transport Canada issued Airworthiness Notice No. C010 Edition 1, dated 10 October 1997, entitled Inspections of Control Systems, which explains the regulations applicable to the maintenance of engine and flight controls and outlines the applicable standards for control systems maintenance. The document emphasizes the requirement that the person performing the dual inspection be independent of the original work and that the inspection include a verification of the range of operation of the control system. In the 4/97 issue of Transport Canada's Aviation Safety Maintainer, the article Exploring the Problem of Misconnected Controls uses the circumstances of another crossed flight control accident (TSB Report No. A97C0089) to raise the question as to why so many people would miss such an important item as the integrity of flight controls. It concludes with a challenge to the reader to develop a methodology that uses all the tools available to avoid lapses that result in mis-rigged controls.Safety Action Following the occurrence, Kelowna Flightcraft Ltd. proceeded with the change of shift work scheduling to a more workable two week shift schedule. Kelowna Flightcraft Ltd. has amended the maintenance training program to include supervisory training for crew chiefs and plans human factors training for all AMEs in the future. Kelowna Flightcraft Ltd. has amended the independent inspection of flight controls to include the inspection and sign-off by a qualified flight crew member. Following the occurrence, Kelowna Flightcraft Ltd. modified the aircraft so that the PTT button was located on the control column. Kelowna Flightcraft Ltd. has recognized the potential for hooking the trim cables in reverse, and future developments of the model 5800 will be designed with the intent of ensuring that the trim cables are significantly staggered to make it difficult to connect the cables in reverse. Kelowna Flightcraft Ltd. is in the process of writing task cards for the removal of assemblies. These task cards will contain a caution note about trim cable connections. Transport Canada issued Airworthiness Notice No. C010 Edition 1, dated 10 October 1997, entitled Inspections of Control Systems, which explains the regulations applicable to the maintenance of engine and flight controls and outlines the applicable standards for control systems maintenance. The document emphasizes the requirement that the person performing the dual inspection be independent of the original work and that the inspection include a verification of the range of operation of the control system. In the 4/97 issue of Transport Canada's Aviation Safety Maintainer, the article Exploring the Problem of Misconnected Controls uses the circumstances of another crossed flight control accident (TSB Report No. A97C0089) to raise the question as to why so many people would miss such an important item as the integrity of flight controls. It concludes with a challenge to the reader to develop a methodology that uses all the tools available to avoid lapses that result in mis-rigged controls.